An optical disk device that records and plays back information on an optical disk such as a CD, DVD, CD-ROM-, DVD-ROM-, CD-R, DVD-R, etc., conventionally has an optical pickup that shines a laser light or other optical spot onto the optical disk and plays back or records information, and a drive device that adjusts the relative position between the optical disk and the optical pickup. In such an optical device, the control system, which includes the drive device, is provided with an automatic adjustment mechanism that adjusts the operation center position of skew, focus, etc. to the optimum position in order to minimize the effect of the jitter that occurs in the playback signal (RF signal) that is detected by the optical pickup, and the skew and focus operation center position is determined by, for example, procedures such as the following.    (1) If there is a relationship as shown in FIG. 10 between the jitter value and the relative position of the optical disk and the optical pickup, a jitter value that is greater than the minimum jitter value by a standard amount is taken as the jitter threshold value. For this jitter threshold value, the upper limit of the error-correctable jitter value is mainly taken as the standard.    (2) Taking point A of FIG. 10 as the standard, while varying the relative position of the optical disk and the optical pickup, one obtains the jitter value at each position and determines the relative position of the two that exceeds a set jitter threshold value, that is, the relative position (edge position) of the upper value of the optical disk and the optical pickup at point B.    (3) When edge position point B is determined in the relative position adjustment of the optical disk and the optical pickup, point C, which is the midpoint between point A and point B, is set as the operation center position in the relative position adjustment of the optical disk and the optical pickup.
However, a problem with such a method of setting the operation center position in the relative position adjustment of the optical disk and the optical pickup is that, because it is taken as a premise that the effect of any disturbance is not received, if the effect of any disturbance is received, it is impossible to set the accurate operation center position corresponding to the jitter characteristics. That is, if a disturbance acts on the optical disk device, such as damage occurring to the optical disk or vibration during measurement of the jitter value, then, as shown by the dotted line in FIG. 10, the jitter value becomes spotwise large, so a point D that exceeds the jitter threshold value arises before reaching point B in FIG. 10, and therefore if the operation center position is computed based on point D and point A, an incorrect operation center position will be set.
It is an object of the present invention to provide an optical pickup position control method that makes it possible, in positioning the relative position of an optical disk and an optical pickup, to set the correct operation center position even if there is an effect by a disturbance, etc.